The present invention relates to a system for converting a signal from a substantially linear transducer detecting a parameter on a motor vehicle electronic fuel injection system, and so enabling parameter acquisition to varying degrees of accuracy. Said conversion system is applied, in particular, for detecting a parameter (in this case, the setting of the throttle regulating air intake by the engine) on an internal combustion engine electronic fuel injection system, of the type comprising an electronic control system wherein a central processing unit receives signals from sensor means and/or transducers detecting major operating parameters, such as engine speed, the setting of the throttle regulating air intake by the engine, and the concentration of exhaust gas components; and wherein said electronic control system provides for controlling final injection preferably via a single-point injection unit: as a function of engine speed and the throttle setting, said central processing unit calculates a basic injection time (determined in open-loop manner) which, depending on various operating conditions, is corrected via parameters supplied by additional sensor means or transducers for detecting at least the engine cooling water and air intake temperatures, and via the signal supplied by the exhaust gas sensor (for determining a controlled injection time in closed-loop manner).
Known injection systems of the aforementioned type differ substantially in terms of the design and operating program of the electronic control system, as a function of the performance demanded of the injection system itself, the components of which are therefore selected and designed on a system cost and required performance basis.
One of the major parameters involved is the setting of the throttle regulating air intake by the engine, which is usually detected by means of potentiometers. Over certain ranges (particularly minimum opening of the throttle), the accuracy of such a system does not always provide for a sufficiently low parameter reading error percentage, which is inevitably reflected in poor injection control timing. One attempt to overcome this drawback has been to replace linear, single-track potentiometers with others producing signals of differing slopes and/or featuring a number of tracks, for enabling different parameter ranges to be read to varying degrees of accuracy. Alternatively, analogue-digital converters have been employed, which receive the signal from the potentiometer, and present a relatively large number of output bits. All these solutions, however, involve considerable cost.